Inverse transport for the verification of the Comprehensive Nuclear Test Ban Treaty

International audienceAn international monitoring system is being built as a verification tool for the Comprehensive Test Ban Treaty. Forty stations will measure on a worldwide daily basis the concentration of radioactive noble gases. The paper introduces, by handling preliminary real data, a new approach of backtracking for the identification of sources of passive tracers after positive measurements. When several measurements are available the ambiguity about possible sources is reduced significantly. The approach is validated against ETEX data. A distinction is made between adjoint and inverse transport shown to be, indeed, different though equivalent ideas. As an interesting side result it is shown that, in the passive tracer dispersion equation, the diffusion stemming from a time symmetric turbulence is necessarily a self-adjoint operator, a result easily verified for the usual gradient closure, but more general

Adjoint backtracking for the verification of the Comprehensive Test Ban Treaty

International audienceAn international monitoring system is being built as a verification tool for the Comprehensive Test Ban Treaty. Forty stations will measure on a worldwide daily basis the concentration of radioactive noble gases. The paper introduces, by handling preliminary real data, a new approach of backtracking for the identification of sources after positive measurements. When several measurements are available the ambiguity about possible sources is reduced significantly. As an interesting side result it is shown that diffusion in the passive tracer dispersion equation is necessarily a self-adjoint operator

Optimisation structurelle des gridshells

National audienceSee http://hal.archives-ouvertes.fr/docs/00/59/29/58/ANNEX/r_Z5N5TCL9.pd

Möbius Geometry and Cyclidic Nets: A Framework for Complex Shape Generation

International audienceFree-form architecture challenges architects, engineers and builders. The geometrical rationalization of complex structures requires sophisticated tools. To this day, two frameworks are commonly used: NURBS modeling and mesh-based approaches. The authors propose an alternative modeling framework called generalized cyclidic nets that automatically yields optimal geometrical properties for the façade and the structure. This framework uses a base circular mesh and Dupin cyclides, which are natural objects of the geometry of circles in space, also known as Möbius geometry. This paper illustrates how new shapes can be generated from generalized cyclidic nets. Finally, it is demonstrated that this framework gives a simple method to generate curved-creases on free-forms. These findings open new perspectives for structural design of complex shells

Prospective créative énergie habitat territoires. Rapport de synthèse

Pour répondre aux enjeux de la transition énergétique, des chercheurs en Sciences Humaines et Sociales, en Sciences pour l’Ingénieur et en Architecture ont collaboré depuis 2013 dans le cadre de l'atelier «Prospective Créative Énergie Habitat Territoires» soutenu par l’ARC Energie de la Région Rhône-Alpes. Ils ont identifié les questionnements sociétaux et professionnels qui nécessitent des approches interdisciplinaires. Des projets de recherche ont été esquissés. Présentés à une cinquantaine d'acteurs de la R&D et de l'innovation urbaine, ils ont fait l'objet de fiches thématiques commentées par des grands témoins :- Coordination des systèmes énergétiques dans les espaces urbanisés- Nouveaux services pour le secteur du bâtiment- Résilience des bâtiments, des réseaux et du territoire- Conception collaborative centrée utilisateur- Généralisation des innovation

Morphological and mechanical investigation of interconnected elastic gridshells

International audienceThis paper describes the structural reinforcement of elastic gridshells by interconnecting several gridshells together. Reference for the present investigation is taken from the composite (GFRP) gridshell structure built for the Forum of the Solidays music festival in Paris in 2011. The principle of interconnection is illustrated with various structures which are generated using numerical toolbox developed by the laboratory for the automatic meshing of free-forms structures on Rhino. Then the effect of the interconnection on the structural behaviour is briefly discussed based on elementary loading cases. Finally, the feasibility of the concept as well as its architectural and morphological potential is show by the construction of a double gridshell prototype. The authors conclude on the possible future developments of such morphologies which could give interesting and unexpected architectures

Inverse transport for the verification of the Comprehensive Nuclear Test Ban Treaty

An international monitoring system is being built as a verification tool for the Comprehensive Test Ban Treaty. Forty stations will measure on a worldwide daily basis the concentration of radioactive noble gases. The paper introduces, by handling preliminary real data, a new approach of backtracking for the identification of sources of passive tracers after positive measurements. When several measurements are available the ambiguity about possible sources is reduced significantly. The approach is validated against ETEX data. A distinction is made between adjoint and inverse transport shown to be, indeed, different though equivalent ideas. As an interesting side result it is shown that, in the passive tracer dispersion equation, the diffusion stemming from a time symmetric turbulence is necessarily a self-adjoint operator, a result easily verified for the usual gradient closure, but more general

Prospective créative énergie habitat territoires. Rapport de synthèse

Pour répondre aux enjeux de la transition énergétique, des chercheurs en Sciences Humaines et Sociales, en Sciences pour l’Ingénieur et en Architecture ont collaboré depuis 2013 dans le cadre de l'atelier «Prospective Créative Énergie Habitat Territoires» soutenu par l’ARC Energie de la Région Rhône-Alpes. Ils ont identifié les questionnements sociétaux et professionnels qui nécessitent des approches interdisciplinaires. Des projets de recherche ont été esquissés. Présentés à une cinquantaine d'acteurs de la R&D et de l'innovation urbaine, ils ont fait l'objet de fiches thématiques commentées par des grands témoins :- Coordination des systèmes énergétiques dans les espaces urbanisés- Nouveaux services pour le secteur du bâtiment- Résilience des bâtiments, des réseaux et du territoire- Conception collaborative centrée utilisateur- Généralisation des innovation

La cathédrale éphémère de Créteil : une couverture ultra légère de 350m2 faite d'une résille de tubes composites en GFRP

National audienceThe Ephemeral Cathedral of Créteil (Paris, France) is a gridshell structure made of composite materials. Built in 2013, this religious edifice of 350m2 is a temporary church meant to gather the parishioners during the two-years renovation of their permanent cathedral. This large-scale prototype (Figure 1) represents a first in the building industry, which still shows excessive apprehension for the use of non-traditional materials such as composites, especially when it comes to structural applications. Based on a previous successful experience [1] the gridshell was prefabricated and erected [2] by the parishioners themselves.Le diocèse du Val de Marne a entrepris la rénovation de la cathédrale Notre Dame de Créteil. Pour la durée des travaux, une structure temporaire de type gridshell en GFRP – Glass Fibre Reinforced Polymer – qui permet d’assurer la continuité des célébrations religieuses, a été réalisée par le bureau d’études T/E/S/S et le laboratoire Navier sur la base d’une expérience antérieure réussie [1]. Cet article présente et détaille la conception et la construction de ce bâtiment (Figure 1) en place depuis 2 ans. Ce prototype de grande ampleur, construit par les paroissiens eux-mêmes [2], constitue une première dans le secteur de la construction qui reste encore très fermé à l’utilisation des matériaux non traditionnels, en particulier lorsqu’il s’agit d’applications structurelles

From shape to shell: a design tool to materialize freeform shapes using gridshell structures

International audienceThis paper introduces and explains the design process of a gridshell in composite materials built in Paris in 2011 for the festival Soliday. A brief introduction presents the structural concept and the erection methodology employed. It explains why composite materials are relevant for such applications. Following this practical case, the whole process from 3D-shape to real-shell is then detailed. Firstly, the shape is rationalized and optimized to smooth local curvature concentrations. Secondly, a specific computing tool is used to mesh the surface according to the compass method. This tool allows designers to look for optimal mesh orientations regarding the elements curvature. Finally, a full structural analysis is performed to find the relaxed shape of the grid and check its stability, strength and stiffness under loads. The authors conclude on the overall relevance of such structures